Chronic dialysis has been performed on patients with kidney failure since the early 1960's. A dialyzer is a device for cleansing blood through hemodialysis by a process of diffusion and/or convection of waste products, dissolved solutes and fluid from the blood across a semi permeable membrane into a dialysis solution known as dialysate. A dialysis system is an assembly that includes the dialyzer and associated equipment to support the dialyzer, such a plumbing and pumps.
Diffusion is the principal mechanism in which dialysis removes waste products such as urea, creatinine, phosphate and uric acid, among others, from the blood. A differential between the chemical composition of the dialysate and the chemical composition of the blood causes the waste products to be drawn through the semi-permeable membrane from the blood into the dialysate. Ultrafiltration is a process in dialysis where fluid is caused to move across the membrane from the blood into the dialysate for the purpose of removing excess fluid from the patient's blood stream. Along with water, some solutes are also drawn across via convection rather than diffusion. Ultrafiltration is a result of a pressure differential between the blood compartment of the dialyzer and the dialysate compartment of the dialyzer where fluid will move from a higher pressure to a lower pressure. In some circumstances, by design or unintentionally, fluid in the dialysate compartment is higher than the blood compartment, causing fluid to move from the dialysate compartment into the blood compartment. This is commonly referred to as reverse ultrafiltration.
It would be convenient for a patient to be able to perform dialysis in his or her home. Unfortunately, current dialysis systems are large in size, making them generally unsuitable for use in a patient's home. Current dialysis systems are also energy-inefficient in that they use large amounts of energy and require enormous amounts of water for proper use. Although some home dialysis systems are available, they generally use complex flow-balancing technology that is relatively expensive to manufacture and most systems are designed with a system of solenoid valves that create high noise levels. As a result, most dialysis treatments are performed at dialysis centers.